Chapter 5 Heredity and Genetics

Dimples

Heredity Traits – things that make a person unique Eye color and shape, nose shape, cheekbone structure, skin color, hair color etc Heredity – The passing of traits from parent to offspring

Genetics Genes on chromosomes control the traits that show up in an organism Alleles – the different forms of a trait a gene might have health/geneticsgrowthandde velopment/genetics/ health/geneticsgrowthandde velopment/genetics/

Genetics! During meiosis, a pair of chromosomes separates and the alleles move into separate sex cells Each sex cell now contains one allele for each trait

Genetics!! Genetics – the study of how traits are inherited Gregor Mendel – the father of genetics The first to use math and probability to explain heredity and trace one trait for several generations

Hybrids. And I don’t mean Prius Hybrid - receives different genetic information (different alleles) for a trait from each parent Dominant allele – covers up or dominates the other trait Recessive allele – the trait is not expressed; it seems to disappear Purebreds – an organism that always produces the same traits generation after generation

Square Dancing! Probability helps you predict the chance of something happening A Punnett Square can help you predict what an offspring will look like Capital Letters stand for dominant alleles Lowercase Letters stand for recessive alleles

Complete this Punnett Square Genes for height of plants:  T =  t = What are the chances that the plant will be tall? What are the chances that the plant will be short?

GENO and PHENO Genotype – the genetic makeup of an organism. All the genes! Homozygous – an organism with two alleles for one trait that are the same. (Written TT)

GENO and PHENO Heterozygous – an organism with two alleles for one trait that are different (Written Tt) Phenotype – the way an organism looks and behaves as a result of its genotype

Review How do heredity and genetics explain why people are different? What’s the difference between a dominant allele and a recessive allele?

Questions People are hybrids; we receive different genetic information from each of our parents. Our parents carry different alleles for the same trait. These alleles can combine in different ways to create different traits in people. A dominant allele is expressed if an allele pair is homozygous or heterozygous. A recessive allele is expressed only when an allele pair is homozygous recessive

Genetics Since Mendel Incomplete Dominance is a situation where neither allele is dominant over the other The phenotype produced is intermediate between the two parents

Incomplete Dominance With incomplete dominance, a cross between organisms with two different phenotypes produces offspring with a third phenotype that is a blending of the parental traits.

Multiple Alleles Some traits are controlled by more than two alleles More than two alleles that control a trait are called multiple alleles Traits controlled by multiple alleles produce more than three phenotypes

Polygenic Inheritance Polygenic Inheritance occurs when a group of gene pairs acts together to produce a trait Height Eye color Skin color Hair color is determined by 3-6 pairs of genes

Environmental Influences Genes determine many of your traits, but you might be able to influence their expression by the decisions you make. Example: Some people might be more prone to skin cancer than others. Limit sun exposure; lessen risk of cancer

Human Genes and Mutations Mutation – when gene changes and results in a trait being expressed differently Ex: A butterfly’s offspring being different colors or blending in better with environment Genetic disorders

Chromosome Disorders Every organism has a specific number of chromosomes that needs to be inherited Mistakes in meiosis can give too little or too many chromosomes Problems can occur if the wrong number of chromosomes is inherited Changes in chromosomes are usually fatal Some diseases are the result of chromosome changes; Down’s Syndrome

Recessive Genetic Disorders Some diseases are caused by two recessive genes carrying a mutation The 2 heterozygous parents don’t express the disease because their dominant gene covers it up Child expresses the disorder because each infected parent gave their infected recessive gene Ex: Cystic Fibrosis

Gender Determination Male Chromosomes: XY Female Chromosomes: XX

Sex-Linked Disorders Some inherited disorders are linked to the X or Y chromosomes Example: Hemophilia is located on the X chromosome Males only have 1 X chromosome, so if their X has the hemophilia gene, it gets expressed Females have 2 X chromosomes, so they have to have the hemophilia on each X chromosome to express it

Why is Genetics Important? Genetic Engineering Biological and chemical methods to change the arrangement of DNA Helps to produce large amounts of medicine Improve crop production

Gene Therapy A normal allele is replaced in a virus and then delivers the normal allele when it infects its target cell Gene Therapy helps to cure some inherited diseases